Bottom Line:
In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation.Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide).Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community.

Affiliation: Department of Chemical Engineering, Stanford University, Stanford, California, United States of America.

ABSTRACTThe selection of an appropriate substrate is an important initial step for many studies of electrochemically active materials. In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation. Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide). We determine the inert potential window for each substrate/electrolyte combination and make recommendations about which materials may be most suitable for application under different experimental conditions. Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community.

Mentions:
The electrochemical reactivity data for our stainless steel 304 samples are presented in Figure 7. In the sweeps in the cathodic region, no features are observed until the onset of the HER at −0.30 V vs. RHE in H2SO4. The HER activity increases substantially with cycling, possibly due to surface restructuring and/or the reduction of the surface oxide, and an oxidative peak (denoted a in Figure 7) appears in the final several cycles. This feature has previously been attributed to the oxidation of hydrogen atoms absorbed within the stainless steel during the HER [44]. In NaAc, we observe a small reductive feature at −0.04 V vs RHE that likely corresponds to native oxide reduction. This feature decreases in size with repeated cycling, but limits the cathodic inert range to 0.05 V vs RHE. The only other reductive feature corresponds to the HER, which is first observed at approximately −0.73 V vs. RHE. The HER activity again increases slightly with cycling. In NaOH, we observe an oxidation/reduction couple with peaks at 0.26 and 0.00 V vs. RHE and very small currents of less than 10 µA/cm2. This couple likely corresponds to nickel oxidation and reduction [45]. The inert potential range extends to −0.43 V vs. RHE, where the onset of the HER is initially observed. The HER activity increases slightly with repeated cycling.

Mentions:
The electrochemical reactivity data for our stainless steel 304 samples are presented in Figure 7. In the sweeps in the cathodic region, no features are observed until the onset of the HER at −0.30 V vs. RHE in H2SO4. The HER activity increases substantially with cycling, possibly due to surface restructuring and/or the reduction of the surface oxide, and an oxidative peak (denoted a in Figure 7) appears in the final several cycles. This feature has previously been attributed to the oxidation of hydrogen atoms absorbed within the stainless steel during the HER [44]. In NaAc, we observe a small reductive feature at −0.04 V vs RHE that likely corresponds to native oxide reduction. This feature decreases in size with repeated cycling, but limits the cathodic inert range to 0.05 V vs RHE. The only other reductive feature corresponds to the HER, which is first observed at approximately −0.73 V vs. RHE. The HER activity again increases slightly with cycling. In NaOH, we observe an oxidation/reduction couple with peaks at 0.26 and 0.00 V vs. RHE and very small currents of less than 10 µA/cm2. This couple likely corresponds to nickel oxidation and reduction [45]. The inert potential range extends to −0.43 V vs. RHE, where the onset of the HER is initially observed. The HER activity increases slightly with repeated cycling.

Bottom Line:
In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation.Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide).Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community.

Affiliation:
Department of Chemical Engineering, Stanford University, Stanford, California, United States of America.

ABSTRACTThe selection of an appropriate substrate is an important initial step for many studies of electrochemically active materials. In order to help researchers with the substrate selection process, we employ a consistent experimental methodology to evaluate the electrochemical reactivity and stability of seven potential substrate materials for electrocatalyst and photoelectrode evaluation. Using cyclic voltammetry with a progressively increased scan range, we characterize three transparent conducting oxides (indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide) and four opaque conductors (gold, stainless steel 304, glassy carbon, and highly oriented pyrolytic graphite) in three different electrolytes (sulfuric acid, sodium acetate, and sodium hydroxide). We determine the inert potential window for each substrate/electrolyte combination and make recommendations about which materials may be most suitable for application under different experimental conditions. Furthermore, the testing methodology provides a framework for other researchers to evaluate and report the baseline activity of other substrates of interest to the broader community.